Plants never cease to amaze the researchers who study our planet’s greenery. With every new impressive discovery about the complex workings of plants,1,2 the more we realize how little we know about them.
This is especially so in relation to roots, which, being underground, have traditionally been more difficult to study than above-ground parts (leaves, stems and flowers).
However, with improved technology, the mysteries of root growth are slowly coming to light.
For example, using sophisticated video imaging techniques, a research team led by University of Wisconsin botanist Simon Gilroy has been able to view the growth of delicate extensions of individual root cells, known as root hairs.3
There are literally millions of these elongated skinny projections covering plant roots. It’s long been realised that root hairs hugely increase the surface area of plant root systems, thus increasing the volume of soil from which water and mineral nutrients can be obtained by the plant. But precisely how root hairs form and grow has remained a mystery.
To Gilroy and his team’s surprise, when they trained their cameras on the hairs, they did not witness the slow, steady lengthening they had expected. Instead, they saw the root hairs undergoing rhythmic pulses of growth every 20 seconds or so. Further investigation linked the pulses to rapid changes in pH (acidity/alkalinity) at the root hair tip and also to the levels of certain reactive chemical compounds.
The findings show that plants are not slow or static, but far more complex and sophisticated than imagined.
“Plants are actually much more dynamic than you’d think by looking at them just sitting there, soaking up the sun,” Gilroy says.4 In fact, plants are responding to cues on timescales of seconds to milliseconds—a rapidity usually associated only with animal responses.
What’s more, as Gilroy explained, unlike animal cells, enlarging plant cells have to contend with a cell wall made of cellulose, which is, weight for weight, stronger than steel. The reinforcing strength of cellulose stops the cell bursting from the tremendous water pressure (turgor) inside. But for the tip of the root hair to grow, the cell must somehow make the cell wall there just flexible enough to stretch from the internal pressure without bursting. It must then quickly strengthen the wall directly behind the tip once extension has occurred….
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